The present invention relates to apparatus for regulating the amounts of fluid which is supplied by a variable-delivery pump and for regulating the pressure of such fluid.
It is already known to adjust the rate of delivery of a variable-delivery pump, e.g., a vane pump or a rotary piston pump, by resorting to a pair of pistons having different diameters and serving to change the position of an actuating element (e.g., a slide block) which thereby changes the amount of fluid that issues at the outlet of the pump. It is also known to connect the cylinder chambers or bores for the pistons with the outlet of the variable delivery pump and to provide a regulating valve which can change the pressure of fluid in one of the cylinder chambers. As a rule, the regulating valve has a reciprocable valve member or spool which is biased in one direction by a helical spring or by other suitable resilient means.
It is also known to associate a variable-delivery pump with several control valves which can be actuated individually or simultaneously to thereby change or limit the rate of fluid flow from the outlet of the pump and/or the pressure of fluid. Such valves render it possible to adjust the pump for operation under several different circumstances, e.g., to supply fluid to several consumers (either simultaneously or at different times) even if the consumers must receive fluid at different rates and/or pressures.
A drawback of presently known apparatus which are used to regulate the pressure and/or rate of fluid flow from a variable-delivery pump is that, in the absence of extremely costly, complex and sensitive auxiliary equipment, such apparatus must maintain the pressure of fluid at a constant or nearly constant value while the rate of delivery varies within a relatively narrow range, or that the rate of delivery remains constant while the apparatus changes the pressure of fluid within a narrow range. This affects the versatility of variable-delivery pumps which are associated with and controlled by the just-described regulating apparatus.